1. Field of the Invention
This invention relates generally to reciprocating wipers, e.g., windshield wipers, and, specifically, to windshield wipers having two or more blades which have formations therein which permit flow of liquid, e.g., water, through the blades in one direction of movement of the wiper, but not in the other.
2. Related Art
Known wipers usually comprise one or more resilient rubber blades mounted on an arm which reciprocatingly sweeps the blades sideways across the surface of a window, vehicle windshield, headlight lens or other formation. As the blades move across the surface, they push water or other liquids on the surface sideways until the arm reaches the limit of its travel, discharging an accumulation of water at the point where the arm stops and reverses its motion. The result is a fan-shaped cleared arc on the surface which is swept clear of water, at least temporarily. In a typical vehicle or aircraft windshield arrangement, there are two reciprocating windshield wiper assemblies, one for the driver or pilot and one for the passenger or co-pilot. One difficulty with this arrangement is that each reciprocating wiper assembly at the “inside” end of its travel path pushes some or all of the water it has cleared into the cleared arc of the adjacent wiper assembly. (The “inside” end of the travel path of the wiper assembly is the end of its travel which is adjacent to or overlaps the cleared area of the adjacent wiper assembly.) The accumulated water pushed into the cleared arc of the adjacent assembly reduces visibility through a windshield or the like and, especially on the driver's or pilot's side, presents a hazard. Removal of the accumulated, pushed water from the windshield is accomplished only when the accumulated water runs off the bottom and sides of the windshield or, in moving vehicles, is pushed off the upper edge of the windshield by aerodynamic pressure. The consequent reduction in visibility can be significant, especially in very heavy downpours of rain.
It is well known in the art to provide two or more parallel wiper blades on a single wiper arm to increase the efficiency of the wiping action, as shown by the following patents.
U.S. Pat. No. 5,168,595, issued to James L. Naylor, Jr. on Dec. 8, 1992 and entitled “Windshield Wiper Blade and Assembly”, discloses one such system. A single wiper arm assembly 20 (shown in FIGS. 1 through 7) has an elongated blade carrier assembly 36 pivotally mounted to the arm 24, and first and second blades 26 and 27 mounted on the blade carrier assembly 36.
U.S. Pat. No. 4,745,653, issued to Bedrich V. Bliznak on May 24, 1988 and entitled “Wiper/Scraper/Washer Blade for Windows on Transportation Means”, discloses a multiple-edged blade 1 (shown in FIG. 1) having two blades of different cross sections in contact with the surface to be cleaned, the smooth blades having a serrated appearance in cross-sectional view.
U.S. Pat. No. 4,567,621, issued to Robert L. Alley, Jr. on Feb. 4, 1986 and entitled “Composite Windshield Wiper Assembly”, discloses a wiper blade assembly A (shown in FIG. 1) having a pair of spaced wiper blade elements 42, 44 having thin resilient wiping edges 42a, 44a. A scrubbing block 50 occupies the entire space between the wiping blade elements and protrudes at 52 past the wiping edges 42a, 44a. 
U.S. Pat. No. 4,339,839, issued to Robert E. Knights on Jul. 20, 1982 and entitled “Windscreen Wipers”, discloses (see FIG. 1) a windscreen wiper having a pair of spaced parallel wiping lips 22 bounding a space 28 in which is a bristle 32.
U.S. Pat. No. 3,916,473, issued to Zelmer L. Williams on Nov. 4, 1975 and entitled “Wiper for Windshields”, discloses (see FIG. 6) a single longitudinal blade 38 provided with a longitudinal groove 40 running substantially the length of the blade 38. An aperture 42 in the blade base 36 permits feed of a fluid, such as windshield washer fluid, to the groove 40, from whence it flows to the windshield via passages 72 which run from the base 36 of the blade to the windshield.
U.S. Pat. No. 1,441,593, issued to Harry L. Lavietes on Jan. 9, 1923 and entitled “Windshield Cleaner”, discloses a windshield wiper (see FIG. 1) having multiple strips 16 held in a pair of longitudinal grooves 15.
U.S. Pat. No. 1,370,910, issued to Julius Pederson on Mar. 8, 1921 and entitled “Windshield Cleaner”, discloses in FIG. 1 a windshield cleaner having wiper strips 11 held in channels 16 of wiper bar 10.
French Patent 2,373,426 issued to Heuliez, discloses in FIG. 4 dual-blade windshield wipers designed to move horizontally across a windshield in linear, parallel movement.